Sunday, September 11, 2011

Can machines think?

These are my impressions after reading Alan Turing's 1950 treatise in MIND on the subject of 'Can Machines Think?'

As i continue to read the articulation of thinking machines by Turing, it seems so incredible that he should have conceived such far reaching ideas as early as 1950!

An example of 'far reaching' would be in his definition rather the lack thereof of a pinning down means by which thought in the machine may be sought and its similarity to the fashion in which humans are said to 'think'. I quote "May not machines carry out something which ought to be described as thinking but which is very different from what a man does? This objection is a very strong one, but at least we can say that if, nevertheless, a machine can be constructed to play the imitation game satisfactorily, we need not be troubled by this objection".
My own notes at the time that I read this were as follows :
" he seems to have forseen that the mechanism of 'thought' in the machine is unlikely to be of the same kind as in a human being and chooses to ignore it.
If say, a machine were to have used solely machine learning and data mining as a method to find the answers to all the questions of the interrogator, Turing would not have minded it, for he has chosen to give weightage to the ends and not the means. "

Then we come to his definition of the digital computer as a machine that can do anything that a human computer can do. Though, I yet wonder what exactly the 'human computer' is meant to imply. Could it be that in the post world war 2 era, the code breakers et all who crunched numbers are the 'human computers'. But by mentioning this, I deviate from my main intention. His definition of the digital computer is legendary. He states that it should have three components viz.
1. store
2. executive unit
3. control unit

I have also found what my previous job was all about. As a coder/programmer I now know what programming is actually supposed to mean 'constructing instruction tables is programming'.

He makes a remarkable comment about the notion that scientists always proceed from well-established fact to well established fact without making use of 'unproved conjecture'. In his opinion this is a fallacy. He further notes that as long as fact and ungrounded conjecture are stated upfront, no harm can result from the use of conjecture for it may even lead to new lines of research.

This line I am yet to understand, but he states that his opinion of the original question of 'Can machines think?' is that 'it is too meaningless to deserve discussion'.  !!! I think he might mean that 'Can machines think?' is irrelevant, but 'Are there imaginable discrete state machines that can do well in the imitation game' is what it should be replaced with.

He has discussed counters to some 8 arguments that stem from diverse areas such as philosophy, Lady Lovelace, Mathematics and even ESP!
This is where I found out that ESP has three forms viz. telepathy, psycho-kinesis, clairvoyance and precognition! His argument against ESP doesn't seem to be very confident. I believe that he did not like the idea of ESP being 'around' despite science and not bothering anyone as long as they chose to ignore it. Albeit he admitted that it might be of special consequence in the particular question of thinking machines. In any case, he seems to have left the doubt lingering (perhaps much to his dislike!).

He has compared the mind to the skin of an onion. To reveal the inner working, you would need to peel off the layer of skin. In doing so, one would reveal yet another layer to be peeled off. I'm not sure how this ties in with the paragraph of learning machines!
It seems obvious to us now, but the leap that he made from 'let's programme a machine to play the imitation game to mimic an adult human brain to 'let's programme a machine to simulate a child's brain and let it learn via education to become an adult brain' is fantastic! Machine learning's roots!
He admitted that a child machine cannot be subjected to the same teaching/education process that a human child is. Further, do we need to give it legs, eyes and ears? He dismisses the need by citing the example of Helen Keller!!!

He talks about punishment-reward systems; again the roots of reinforcement learning!
He also talks about how the teacher would be largely ignorant of the internal working of the machine. Unlike the previous idea of a machine having to be told exactly what it needs to do (the progamming part!), and as a counter to Lady Lovelace's argument of a machine being unable to create and being able to do what its been told to do, this new learning machine would be creating and be doing more than it is programmed to do (since it is learning!).

In his conclusion he mentions that there are two ways in which he thinks machines should be competing with humans.
1. Abstract activity like playing chess
2. Give a machine the best sense organs that money can buy and let it learn as a child does.

He admits to not knowing which of the two approaches is the ideal one and that both should be tried.

29 pages of a very interesting read indeed!

Thursday, March 24, 2011

Artificial Trees!

Now, this is an interesting idea! Given hat man is entirely hopeless at protecting the environment and compelled by some inner voice to make ash out of any remaining beauty in his path, this concept might actually take off, if only for the selfish need that we have for oxygen.

The idea is this - create artificial trees that would absorb CO2 out of humidity by a technique called humidity swing (more on this later).  They would also be equipped with solar panels to create energy to drive this process. Further, a see-saw below the tree would encourage people to play on it thereby creating more energy to be diverted to the absorption process. Excess energy would be used to light up the tree at night which would then serve as a pretty street light!
Hmmm....thats the first thought that came to my mind.
And the next one, what is this humidity swing process anyway?
and the third, what would the tree do with the CO2 it extracts from the humidity?
Oh, and another thing, the tree would be made out of recycled plastic from old bottles and what not.

To the second thought....A paper by Klaus Lackner and Allen Wright from Columbia University proposes a method of CO2 capture using a humidity swing sorbent.
Two things here,
1. Humidity swing is the process of raising the relative humidity (called RH ;) )  to a large value for a while and then returning it to normal value.
2. A sorbent is basically an absorbent, a material that absorbs another.
So this is how it works...
1. A dry resin absorbs CO2.
This dry resin consists of +ve ions fixed to a polymer matrix and free -ve ions (OH-)
OH- + CO2 -> HCO3-

2. The resin is wet with water.

3. When the CO2 saturated resin reacts with water it releases CO2 at a higher pressure. The resin is then ready to be used again as in step 1.
2HCO3- -> H2O + CO2 + CO3-
This the resin regeneration phase.

4. Drying of the resin
When the water and CO2 are released, the RH of the resin drops to the original value and it is ready for reuse.

Now coming to the question of the CO2 that would be stored and then released....where would it be stored? What happens to the CO2 when it becomes time to regenerate the resin? Will the saturated resin be unsaturated in an enclosure that traps the CO2 when it is released from the resin? If so, wha would they do with it once captured? Release it into space? solidify it and bury it?
And a new question that has popped into my head just now....where's the O2 in this process generated from? I wonder if the news articles were misleading.... Rather an unsatisfactory understanding at this stage...but when I do get more detailed information, I'll be sure to update :)

Links :
The news article in the bangalore mirror -
The paper -

Thursday, March 17, 2011

Planes can fly!

It all started out with that blasted xkcd comic! It came up at random and it got my fingers itching to know the answer. So as is my way, i spent an afternoon digging up information, when i finally hit on this gem.

There are a couple of things that need to be noted here :
1. Bernoulli effect : "when the speed of horizontal flow through a fluid increases, the pressure decreases" quoted from wisegeek . I especially liked the analogy about a fluid flowing through a narrowing pipe. It speeds up, but considering that there's no change in mass or gravity, the pressure behind the fluid must have to increase compared to that in front to push the fluid faster.

2. Cambered airfoil : basically this means an unsymmetrical airfoil.

3. To avoid the suspense :-
  • airplanes CAN fly upside down
  • lift is not because of airfoil shape (What a world do we live in when we can't even begin to trust our own school textbooks!), though it does on ;)
  • airfoils can be symmetrical, asymmetrical and even flat :D
4. Two criteria are essential to an airfoil :-
  • It should have a sharp trailing edge
  • the trailing edge should be aimed diagonally downward
Now to the explanation.
Oh wait, first off, forget what you read in school about airfoil shape being responsible for anything....hmm, next i'll have to find out what the different shapes are really for!
One answer that I know of is : the camber is there to prevent stall (reduced lift from upper surface compared to lower surface) and to allow a plane to fly at lower speeds

Two explanations of the lift
1. Newton's 3rd law and Coanda effect
2. Bernoulli effect
According to the source that I've cited, both explanations are equally viable and are not competing in any way...they're just both right!
So, on to the first :-
When an airfoil (remember that this can even be a plank of plywood, though it wouldn't be a very good one) goes through the air at a positive angle of attack, both the upper and lower surface of the airfoil are responsible for the lift; a greater portion of which is from the upper surface. The air along the upper surface is stuck to the surface or attached to it because of the Coanda effect (fluid or gas stream will hug a convex contour when directed at a tangent to that surface) and hence it flows along the upper surface and since the trailing edge of the wing is aimed downwards (see point 4 above), the air is pushed downwards resulting in a downwash. By Newton's 3rd law, this produces an upward force on the airfoil. Now, to the lower surface. At the +ve AoA (fancy abbr for angle of attack), the air is pushed downwards by the lower surface, hence the air pushes upwards. These two forces, combine to produce lift. YAY!

Without the downward deflection of air, the AoA is irrelevant since lift won't be created.

The leading edge of the airfoil splits the airflow current into two, sending one over the upper edge, and another below the lower edge. If the airfoil has a +ve AoA OR if the airfoil has a classic shape (like we've always been taught), then the stream of air travelling above the airfoil will be well over the upper edge.
Enter Bernoulli...The air flow on the upper edge, since it travels in an arc well over the upper edge, causes the creation of a pocket of low pressure. Air therefore rushes in to fill this low pressure area. However, the air flow along the lower edge, since it collides with it, causes a region of high pressure to develop. This high pressure region slows the air stream on the lower edge down. The pressure differential generates a lift.
But the difference in air velocities over the upper and lower edge is caused because of the pressure difference, and not the other way around.

Now that that is all sorted out, lets move on to the airfoil shapes....
1. The classic shape
From above, we see that the classic shape is good in the case we want large lift even at low speeds. Also, it reduces drag significantly.
2. A flat wing
This would require a much larger AoA to generate the required lift. Though, it would still develop the pressure differential and downwash in the same explained manner. But the increased AoA would mean a greater drag.
Helicopter blades are nearly flat. This is preferred because drag is almost not an issue for them. What is required is a maneuverable AoA and airspeed. This is encouraged by nearly flat or tear-drop shaped (symmetrical) blades.
3. symmetrical wings
A symmetrical or tear drop shaped wing (like most planes do), will resemble the classic shape when positioned appropriately. This is why planes can fly upside down. Both lifting phenomenon still work. 

A really good explanation is quoted below from

"Airfoil sections are of two basic types, symmetrical and nonsymmetrical.
Symmetrical airfoils have identical upper and lower surfaces. They are suited to rotary-wing applications because they have almost no center of pressure travel. Travel remains relatively constant under varying angles of attack, affording the best lift-drag ratios for the full range of velocities from rotor blade root to tip. However, the symmetrical airfoil produces less lift than a nonsymmetrical airfoil and also has relatively undesirable stall characteristics. The helicopter blade (airfoil) must adapt to a wide range of airspeeds and angles of attack during each revolution of the rotor. The symmetrical airfoil delivers acceptable performance under those alternating conditions. Other benefits are lower cost and ease of construction as compared to the nonsymmetrical airfoil"

Other sources were :

Monday, March 14, 2011


For the last year and a half, I've been subscribed to a marvelous set of podcasts that i religiously follow. In case, my laptop ever crashes for no given reason or I quit my current place of work (yay!) and so have to give up my mac, on whose iTunes I'm currently subscribed or if a giant meteorite should happen to destroy well....something anyway, here's a record of my favourite podcasts :
  1. Stuff you should know (
  2. The Naked Scientists (
  3. From our own correspondent (
  4. Brain Stuff (
  5. 60 second Earth and 60 second Science ( and
  6. A point of view (
  7. The science of everything (
  8. Quirks and Quarks (
And here are the podcasts that I wish never died a slow death :'( I miss you guys...please come back!!!
  1. The Thought experiment (
  2. Discovery Friday news feedbag

Tuesday, January 4, 2011

The Two-Way Mirror

I went to a friend’s house on new year’s day and she took me on a little tour of her house. Her balcony, curiously enough, had a stepper (exercise machine) and was enclosed with a two-way mirror. For the rest of the evening, I couldn’t sit still! I had to figure out how the bloody thing worked!
So, as soon as I got home, I logged on and checked it out online and walaa! The mystery of the working of the two way mirror was discovered! :D
There are two sides to a pane of glass. The front and the front-of-the-back.
In conventional mirrors, it is the front-of-the-back which is silvered. Therefore, when light falls on it, it is almost completely reflected, leaving anyone on the other side of the mirror with nothing to look at but the painted back end.
However, in a two-way mirror, it is the front that is covered in a very sparse ( not dense ) coating of acrylic or a reflective material. Further, the lighting of the two rooms that this two-way mirror forms an interface between is very important.
Let ‘A’ and ‘B’ be two people...’A’ the prisoner and ‘B’ the cop.
A||||B represents the two people and the mirror in between them.
The room in which ‘A’ is present is very brightly lit while ‘B’’s room is dimly lit. Now, the coating on the mirror, is very thin and would cover say half the molecules on the front surface of the mirror, allowing quite a bit of light to pass through.
Since A’s room has so much light in it, say half the light passes through the two-way mirror into B’s room, allowing B to view A through what seems now like a tinted glass, which is what it exactly is! But B’s room is dimly lit, therefore, the light passing through to A is insufficient for A to see B. A ends up seeing on the light that is reflected off the coating, which is an image of itself. Hence, to A, the two-way mirror seems like a mirror!
If the lighting of the two rooms were to be interchanged, i.e. A’s room be made dim and B’s room be made bright, the situation would be reversed. That is why in cop stories on TV, the prisoner in his room, would try to cup his hand over his eyes and peer through the glass, thus obstructing the bright light of his room so that he may see through! And in the case of my friend’s balcony, she wouldn’t want other people in the surrounding flats to be able to see her on the stepper during  the morning hours when it is much brighter outside ( courtesy the sun :) ) while at night, there wouldn’t be much light in the sky anyway to let anyone look in.

A good way to figure out if you’re stuck at the wrong end of a two-way mirror is to put your finger up against the mirror. If the reflection of your finger is right up against your real finger without any gap, then your up against a two-way mirror. In a conventional mirror, you would notice a gap between your finger and its reflection, because the reflective coating is on the front-of-the-back of the mirror and not on the front ( unlike a two-way mirror ).